The present invention relates to an improvement of a deceleration controlling apparatus for an elevator.
It is a duty to equip a terminal stopping device in order to maintain the safety of an elevator.
The terminal stopping device is to land the cage on the terminal floor in safety when the cage approaches near the terminal floor even though the cage could not be decelerated by a normal stopping means because of certain failure.
FIG. 1 shows the principal.
In FIG. 1, the curve AC is a speed curve given by a normal stopping means; and the curve BC is a speed curve given by a terminal stopping device.
During the normal operation, the cage is decelerated at suitable decelerating speed as the curve AC by the below mentioned normal stopping means. However, when the cage runs as the curve AB because of certain failure, the normal stopping means is switched to the terminal stopping device. The cage is further decelerated as the curve BC to land on the terminal floor.
As it is clear from the description, the deceleration as the curve BC is remarkably higher than the deceleration as the curve AC as about two times in usual.
In the overload descending operation of the cage, a significantly large regenerative current is passed through the motor in said condition. The fact is shown in FIG. 2.
In FIG. 2, currents in an armature of a DC motor for driving the cage of the elevator are shown and the curve (a) designates the current in the normal deceleration and the curve (b) designates the current corresponding to that of the deceleration by a terminal stopping device.
Recently, a static Leonard system using a thyristor has been used for a controlling apparatus of the elevator. In order to pass such large current during the terminal stopping, it is necessary to use a thyristor which is durable to the large current and it is uneconomical.
There is also a possibility of causing a flash-over of the motor to such large current because of a failure of commutation.
On the other hand, when the decelerating speed during the terminal stopping, is decreased, the curve AC approaches to the curve BC whereby the terminal stopping device is actuated in many times by slight drifts. In usual, the feeling in the terminal stopping is significantly inferior to the feeling in the normal stopping. Accordingly, such erroneous actuations are disadvantageous.